1. Field of the Invention
The invention relates to a roll head for a planetary crossrolling mill wherein the mounting and adjustment of the shafts bearing the tapered rolls is in cantilever fashion, which produces an axially and radially compact structure, that is to say, in the latter case, a structure which dispenses with components which do not act as direct supports.
2. Description of the Prior Art
Planetary crossrolling mills are used as so-called high-reduction rolling mills for rolling out solid and hollow cross-sections, in particular for marked reduction of cross-section, in order to bring the material to be rolled much closer to the desired final cross-section in a single pass. The rolling forces to be applied are correspondingly high. Planetary cross-rolling mills generally consist of three roll heads each bearing a tapered roll and resting in a rotor with which they revolve round the material to be rolled so that the tapered rolls can make a reduction in the cross-section. For this purpose, the tapered rolls are arranged with their axes inclined to the axis of the material to be rolled and their axes cross the axis of the material to be rolled at a short distance. On a hollow shaft, through which the material to be rolled reaches the tapered rolls, there is located a sun wheel on which there run planetary wheels which drive the respective roll shaft via an intermediate wheel, a tapered pinion and a bevel wheel in each case. The adjustment and obliqueness of the rolls, the diameter of the material to be rolled and the speed of the rotor can only be adjusted for one respective condition to prevent the material to be rolled from rotating about its axis. To prevent the material to be rolled from twisting under other conditions, the hollow shaft traversed by the material to be rolled is accordingly rotated forwards or backwards.
Particular importance is attached to the roll heads revolving round the material to be rolled with the rotor as they are exposed to high rolling forces and high centrifugal forces. The centrifugal forces are directly proportional to the distances at which the components are arranged relative to the axis of the material to be rolled and they increase with the square of the angular velocity, which directly determines the throughput of the rolling mill. As a result, the components, in particular the heavy components, should be arranged at as small a distance from the axis of the material to be rolled, as is permitted by the roll geometry determined by the diameter of the material to be rolled and the reduction of roll passes. For this purpose, a rolling head design of the type disclosed in the proceedings of the ILAFA Rolling Mill Congress, published by the Instituto Latinoamericano del Fierro y el Acero, May 1980, page H 9/10, FIG. 26, has proven advantageous. According to this prior art there are provided a radial bearing and an axial bearing of a very strong design, in which is supported one end of the roll shaft which bears the tapered roll at this end in a cantilever fashion while, at its other end, the roll shaft is rotationally engaged, but axially movably inserted in the bevel wheel of the roll drive mechanism mounted in the roll head housing. A support ring for the axial bearing which is inserted rotatably in the roll head housing and is rotatable for the axial adjustment of the roll is arranged between the bearings (radial and axial bearing) and the bevel wheel. To enable the support ring to rotate, it is coupled via a clutch to the bevel wheel driving the roll, while the support ring is fixed non-rotatably in the roll head housing during rolling via the same clutch. A bush which is provided externally with the adjusting thread and contains the bearings (radial and axial bearing) in its bore acts as a support ring.
The design of the support ring as a bush demands a roll head which is larger by twice the wall thickness of the bush, and, with predetermined roll head dimensions, only permits bearings which must remain in diameter smaller than bearings of maximum conceivable diameters by twice the wall thickness of the bush.